PSI - Issue 78

Emanuele Rizzi et al. / Procedia Structural Integrity 78 (2026) 1420–1427

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Fig. 3. Schematization of the roof bracing system.

4. Failure mechanisms of nave arcades The failure mechanisms depend on the direction of seismic forces, the degree of connection between structural elements, and the boundary conditions provided by the roof structure. The most likely failure mechanisms under in plane (IP) and out-of-plane (OOP) seismic actions in the unstrengthened (U) and strengthened (R) configurations are illustrated in Fig. 4, even though they do not cover all possible scenarios. For example, IP forces may cause the masonry to exceed its tensile strength at the arch sections, potentially triggering arch mechanisms or mixed arch–column mechanisms. However, the discontinuity at the base of the columns and between the columns and the overlying masonry wall, suggests that the column should rotate at the base and in respect to the masonry above. Moreover, the continuity of the masonry within the entire arcade suggests that it undergoes translational motion with minimal or no rotational deformation (Fig. 4a). Thus, the kinematic mechanism is composed of two rigid bodies: block A (the column) and block B (the nave wall portion), connected at hinge C. The double pendulum constraint at top prevents the rotation of block B. The masses involved are those associated with the blocks self-weights ( P A and P B ) and the dead loads from the nave ( P R,1 ) and side aisle ( P R,2 ) roofs. In the configuration IP R (Fig. 4b), the effect of the stiffened side aisle roof is considered by means of elastic springs k t , acting in the horizontal direction.

Fig. 4. Failure mechanisms: (a) IP U ; (b) IP R (c) OOP U ; (d) OOP R .